Chemistry at the Nanometer Scale

Single-molecule fluorescence detection to design “smart” catalysts, graphene semiconductors, covalent organic frameworks for flexible photovoltaic devices, 3-D magnetic-resonance imaging of nanoscale objects, and even more breakthroughs are all coming from one nanoscience research program —Chemistry and Chemical Biology at Cornell University. Here, problem-focused researchers thrive in the collaborative culture at one of the world’s premiere research universities.

At Cornell Chemistry, this supportive, collaborative environment includes resources like the Center for Molecular Interfacing http://cmi.cornell.edu, a National Science Foundation-sponsored Center hosted at Cornell University and the Kavli Institute for Nanoscale Science http://www.research.cornell.edu/KIC/ devoted to development and utilization of next-generation tools for exploring the nanoscale world.

Nationally supported user facilities (the Cornell NanoScale Science & Technology Facility, for example, the Cornell Center for Materials Research, and the Cornell High-Energy Synchrotron Source) give nanoscience researchers the tools they need to do their best work in an interdisciplinary setting.

Among the exemplary research efforts in Cornell Chemistry nanoscience are these:

Designing “Smart” Catalysts

One Cornell Chemistry nanoscience group, led by Peng Chen is developing novel single-molecule methods to characterize and understand the properties of nanoscale materials and biological systems. The Chen group’s microscopic method — Single Molecule Fluorescence Detection — lets them observe the behavior of individual nanoparticles of a catalyst at the resolution of single catalytic events. “Once we understand the fundamental principles that govern catalytic activity,” Peng Chen predicts, “we can begin to think about designing ‘smart’ catalysts that adapt to different conditions.”

Growing Graphene Semiconductors

Another interdisciplinary research group, led by Jiwoong Park uses a variety of advanced tools to explore the synthesis, assembly, and characterization of nanoscale materials and devices, including carbon nanotubes and graphene. They use laser spectroscopy (Raleigh and Raman imaging) to develop novel ‘eyes’ that identify chirality information of individual carbon nanotube molecules with extremely high throughput. His group also develops and characterizes new growth methods for single-atom-thick graphene. According to Professor Park, “We’ve found a simple way to make single-layer carbon semiconducting devices by growing graphene directly on silicon wafer.”

Self-Assembling Flexible Photovoltaics

In the William Dichtel group researchers use the tools of synthetic and supramolecular chemistry to address fundamental challenges in the assembly and integration of nanostructural materials. Recently this approach yielded a new method, Dichtel says, “for self-assembling molecules into covalent organic frameworks (COFs) for stackable, porous, two-dimensional sheets that can become — among other applications — economical, flexible, photovoltaic devices."

MRI at Nanscale Resolution

When the interdisciplinary research group led by John Marohn thinks about organic circuits, solar cells, and macromolecular complexes, “We wonder, ‘What’s really going on down there?’” admits Professor Marohn. To find out, his group has developed scanned-probe methods to examine the nanoscale details of how light leads to current in solar cells — and how charge flows in semiconductor films and devices. “To study individual molecular machines,” Professor Marohn says, “we have invented and are demonstrating new approaches for pushing magnetic resonance imaging to nanometer resolution.”

A World-Class Facility for Students’ Research

At the Cornell Center for Materials Research (CCMR, http://www.ccmr.cornell.edu), director, also a chemistry professor, Melissa A. Hines notes, “Our world-class facilities for determining chemically specific information are second to none in a university setting.”At CCMR, students can image individual defects in single-atom-thick films or determine the atomic-scale chemical composition of fuel cell catalysts in a world-leading electron microscopy facility. They can characterize the spatial distribution of fluorescence with near-field scanning optical microscopes. Or determine the structure of nanoparticles in the x-ray diffraction facility. The facilities are run by full-time staff members, who train students and provide expert consultation.

Cornell has a wide variety of other resources that are critical to chemists working in the nanoscale realm, including an on-campus synchrotron (http://www.chess.cornell.edu) for high-resolution structure determination, as well as a state-of-the-art nanofabrication facility (http://www.cnf.cornell.edu).

With justifiable pride, Professor Hines says: “In addition to our superb facilities, Cornell has outstanding resources for training students in interdisciplinary fields, including a large number of graduate fellowship programs. These programs, such as our newest in Materials for a Sustainable Future, expand the intellectual horizons of our Chemistry graduate students, provide training in important skills such as public speaking and scientific writing, and provide multiyear financial support.”